Dark Matter/Transcript
Transcript A boy, Tim, and a robot, Moby, are in a room staring at each other. It's nighttime, and lightning shows through their window. TIM: I don't care if you are a robot, I'm going to win this staring contest. Lightning strikes and the power goes out turning the room dark. TIM: Whoa, that must have downed a power line. I'll go get some candles. Tim walks a few steps, bumps into something, and falls down. Moby's eyes light up and shine on Tim. MOBY: Beep. TIM: Hey, couldn't you have done that before? Moby clicks his fingers and creates light. TIM: Or, or that? Tim reads from a typed letter. TIM: Dear Tim and Moby, What exactly is this "dark matter" stuff I've been reading about? From, Jonno. TIM: Dark matter is a theoretical substance that makes up much of the universe. The screen is mostly black except for a question mark in the center and a small rectangle in the upper right corner. Inside the rectangle is a sun and other stars. TIM: Scientists still aren't exactly certain that it exists. MOBY: Beep. TIM: Well, like a lot of new ideas in science, there's evidence to suggest that dark matter is out there, just nobody has proven it yet. An image shows two scientists. John Dalton is thinking about atoms in 1808 and Erwin W. Müller is looking at atom-like shapes on a screen in 1955. TIM: That doesn't mean it's just some wacky guess though. Most scientists believed in the existence of atoms long before any had actually been observed. A lot of times in science, you notice the effects of something way before you actually discover it. An image shows astronomer Fritz Zwicky looking through a large telescope pointed at the night sky in 1933. An animation shows Zwicky observing revolving galaxies. TIM: Dark matter was first proposed in the 1930s by Swiss-American astronomer Fritz Zwicky. Zwicky was observing a distant cluster of galaxies when he noticed that something was off. The galaxies were revolving around the center of the cluster faster than they should have been, based on their mass. MOBY: Beep. An animation labeled gravity shows the moon revolving around the earth. More animations show the earth revolving around the sun, the sun revolving around a swirling galaxy, and galaxies revolving around darkness. TIM: Oh, revolving isn't just for planets and moons. Everything in the universe revolves around a center of gravity. An animation shows a man reading a book titled "On Motion" by Galileo. An apple falls onto the man's head. TIM: Gravity is the force that pulls all objects together. A split screen animation shows the earth revolving around the sun on the top, and below it, a moon revolving around a larger blue star., TIM: The more massive an object, the more gravity it exerts on other objects. And the more gravity an object exerts, the faster other objects revolve around it. Zwicky stands in front of a chalkboard with mathematical calculations representing the speed of rotating objects and gravity's force on them. TIM: According to Zwicky's calculations, the galaxies he observed would have to be fourhundred times more massive than they appeared to be in order to be moving so fast. This is known as the "missing mass problem." The dark area with the question mark on it reappears TIM: Zwicky's answer to the problem was dark matter, a special kind of substance that can't be detected by ordinary means like telescopes. In the decade since Zwicky's observations, scientists have found lots of other examples of missing mass in the universe. MOBY: Beep. TIM: No, not all scientists think that dark matter is the source of the missing mass. An animation shows a circled question mark over a background of many question marks. TIM: Even those who think it does exist, don't agree on what dark matter is exactly. But many of them can agree on its characteristics. Dark matter would have to be pretty much invisible. An image shows measurable light, radiation, and radio waves symbolized by circled question marks and waved arrows. All are crossed out showing none of these are present in dark matter. TIM: Unlike the normal matter that makes up the stars and planet it would reflect no light, give off no radio waves, and emit no radiation. An image shows a chart representing the electromagnetic spectrum. A gradient shows a black area, labeled “long wavelength”, extending into a white area, labeled “short wavelength.” Wavelengths are shown in different colors. Radio waves are black, microwaves are dark gray, infrared light are medium gray, visible light are rainbow colors, ultra violet light is light gray, x rays are a lighter gray, and gamma rays are white. TIM: In other words, dark matter would not interact with the electromagnetic spectrum. In fact, it wouldn't even interact with ordinary matter. A dark matter particle would pass right through you, like a ghost. An image shows rotating galaxies. TIM: The only way to detect it, would be indirectly by its gravitational effects on the things we can see, like stars and galaxies. MOBY: Beep. TIM: Well, for example. Astronomers have observed mysterious cases of gravitational lensing. An animation shows a telescope viewing a double star illusion called gravitational lensing. It's caused by a galaxy's gravity in front of a star. A second animation shows the same illusion with nothing between the telescope and the star. TIM: That's when the gravity of massive objects, such as galaxies, bends light creating optical illusions, like double images of stars. But telescopes have shown lensing effects caused by what appears to be nothing at all. MOBY: Beep. TIM: Well, there are lots of different theories about what dark matter is actually made of. An animation shows a symbol for neutrinos moving rapidly. TIM: Some scientists think it's made up of neutrinos, fast moving particles even tinier than electrons. Some think that dark matter is just ordinary matter at really high density, whose gravity is strong enough to keep electromagnetic waves from escaping. An animation shows a flashing orange circle in space that turns into a black circle with a haze around it. The view moves into the dark circle and then a question mark is placed over it. TIM: This kind of dark matter could exist in black holes, collapsed stars that are so dense, not even light can escape their gravity. And some think dark matter is made of particles unlike any we've ever observed. MOBY: Beep. TIM: Yeah, I know. It's kind of weird to hear that scientists don't all agree about something. But that doesn't mean that dark matter is just a random guess, or that science can't give us answers about the universe. An image shows a question mark in a large dark area. TIM: We just haven't gathered enough evidence yet to know for sure what's behind the missing mass problem. Moby raises his hand. MOBY: Beep. TIM: No, I don't think there's any evidence to suggest that it's caused by giant, invisible turtles. MOBY: Beep. TIM: A flying spaghetti what? I have absolutely no idea what you're talking about.Category:BrainPOP Transcripts